Adding a lowercase "z" at the end (Proper form, LOLz, or LoLz to switch between capitals and lowercase as is commonly done by a number of prepubescent horny teens, namely girls) does not necessarily add another word to the acronym. Just like if I were to write to you about "STDs", I would not be talking about Sexually Transmitted Disease Succotash, but rather multiple Sexually Transmitted Diseases.

The Urban Dictionary Mug

In leet speak, plurals are generally denoted by a 'z' instead of an 's', so lols becomes lolz.

2. lolz (v.) - A leet corruption of lols

Treating lol as a verb (to lol), the he/she/it conjugation of lol in the present indicative tense is 'lols', (i.e. I lol, we lol, he lols).
Using the leet practice of replacing 's' with 'z', this is corrupted to 'lolz' (I lol, we lol, he lolz)